1. Field of the Invention
The invention relates to a method for the preparation of 1-terpinen-4-ol, 1(7)-terpinen-4-ol and intermediates thereof.
2. Brief Description of the Prior Art
Terpinen-4-ol is a fragrance chemical possessing a pleasing earthy-green note with a slightly peppery-woody undernote. It is an important constituent of synthetic essential oils, especially geranium, lavender and rose oils and has the desirable effect in all fragrance compositions of enhancing naturalness and diffusiveness. Because of the high cost and uncertainty of supply of the natural product, isolated from tea tree oil, synthetic routes to terpinen-4-ol have been developed, notably via photo-oxidation or epoxidation of terpinolene. Both of these processes suffer from only modest overall yields and multiple chemical steps. The photochemical route requires expensive specialized equipment.
1(7)-Terpinen-4-ol is a little-known isomer of 1-terpinen-4-ol. It is a constituent of rosemary oil but its commercial development as a component of synthetic essential oils is hindered in that the only reported preparation [Indian J. Chem., 1971, 9(9), 899] requires a number of steps, an expensive starting material, and the use of a highly toxic mercury reagent.
The procedure of the present invention has two major advantages over the prior art. First, it is a single step process. Second, it proceeds in high selectivity to obtain either or both the desired 4-ol products. Little or no 1-ol is produced. This procedure has the further advantage that it uses as its starting material a low-valued by-product, 1,4-cineole, generated during the production of pine oil by hydration of the abundant turpentine component, alpha-pinene.